00:00
If we kind of integrate all of the
various receptors that we have,
let’s start with this.
00:06
We have central chemoreceptors and
they are responsive to hydrogen ions.
00:10
We start with central
chemoreceptors because
they are the primary
drive for us to breathe.
00:16
In fact it is kind of interesting
that we breathe because
we have too much CO2 in the
system and hydrogen ions,
not because we need
oxygen on regular basis.
00:27
But this sends feedback to the respiratory
control to start one to breathe.
00:33
We also have peripheral
chemoreceptors.
00:35
These are much more responsive.
00:36
They’re responsive to both oxygen,
carbon dioxide and hydrogen ions.
00:41
We have pulmonary stretch receptors
and we have these various receptors that
are located in the joints and muscles
and these sense
stretch and tension.
00:52
Now, what does the respiratory control
center do with all of these information?
Well, the biggest signal is it
needs to signal the diaphragm
and the external intercostals
and accessory muscles
so that you can inspire
or breathe in.
01:06
Other control factors to the
internal intercostals and
abdominal muscles for you
to breath out or expire.
01:14
This is this whole system
of having the sensor.
01:18
This particular place in the
respiratory control center
that compares and integrates
all this information
and then does an effector
type of response.
01:28
So in the pons, we have something
known as the pneumotaxic center.
01:32
We also have the apneustic center
and the pre-Bötzinger complex,
the dorsal respiratory group neurons
that are very important for inspiration.
01:43
And then the ventral group neurons that
are important for forced expiration.
01:50
The medulla control centers,
the dorsal respiratory group
neurons are going to be
the primary instigators
for us to breathe in.
01:58
And this sets a general rhythm
and frequency of inspiration.
02:04
That feedback is sent to the diaphragm
and the diaphragm contracts,
pulling on the alveoli because
they are mechanically tethered
so they decrease the amount of
pressure and air can flow in.
02:18
There are also these neurons in
the dorsal respiratory group
that have an intrinsic
oscillator in them.
02:24
And what this means is they
start with a low frequency
and gradually build and build
and build and build and build
until it reaches a threshold
and sends information
via the phrenic nerve to
the inspiratory muscles.
02:41
The dorsal respiratory group
neurons also receive feedback
from many of the sensor that
we’ve already talked about.
02:48
And the ventral group
respiratory neurons
are primarily engaged
during forced expiration.
02:54
And so that is a forced
breathing out type of maneuver.
03:03
Now, these apneustic and
pneumotaxic centers.
03:06
Initially, they thought these
were going to be very important
for the control and
regulation of breathing.
03:12
But now, we know them more
as simply accessory centers
that will be involved with
certain types of breathing.
03:20
For example the pneumotaxic
center helps to abate
or limit tidal volume
when you’re breathing in.
03:27
And again, this is
very important because
the fact that the delicate
structures of the lung.
03:33
And they can overinflate which
then can damage those tissues.
03:38
The apneustic centers seem to be primarily
responsible for inspiratory gas.
03:46
Now, there are other structures in the brain
that help govern our breathing frequency.
03:51
These are places like
the cerebral cortex
that you can override the
normal breathing cycle.
03:58
The limbic and hypothalamus also can
override that central pattern generator
and that is done usually
during fear or excitement
or some sort of agitation such
as being chased by a lion.
04:13
Now these two centers, the
hypothalamus limbic system
and the cerebral cortex again can override
the basic rhythm in normal breathing.
04:23
And we all know this because we can
govern how much or how quickly we breathe
for certain period of like,
just like in this example.
04:32
That the person is not going to breathe
until they get their particular way.
04:35
But eventually they will have to breathe
because it will override this particular
hypothalamic and cerebral cortex response.
04:46
So how does this inspiration
and expiration work?
Well, the dorsal respiratory
group neurons are
the primary factors for
you to breathe in.
04:56
They adjust both the frequency
of breathing in and the depth.
05:01
And that is primary
regulated by the diaphragm.
05:04
Now, the ventral respiratory
group neurons of which
there are a couple of
different subsections.
05:09
There’s a rostral. There’s an
intermediate and a caudal section.
05:13
These help control things like the accessory
muscles and external intercostals
as well as abdominal muscles
and internal intercostals.
05:24
And it is this particular
complex that may help generate
the rhythm that the dorsal respiratory
group neurons get feedback for,
which adjusts the rate
and depth of breath.